A right whale feeding just below the surface of Cape Cod Bay offshore from Wellfleet, Massachusetts.
Photograph: Right Whale Research/AP

The dwindling North Atlantic right whale population is on track to finish its breeding season without any new births, prompting experts to warn again that without human intervention, the species will face extinction.

Scientists observing the whale community off the US east coast have not recorded a single mother-calf pair this winter. Last year saw a record number of deaths in the population. Threats to the whales include entanglement in lobster fishing ropes and an increasing struggle to find food in abnormally warm waters.

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The combination of rising mortality and declining fertility is now seen as potentially catastrophic. There are estimated to be as few as 430 North Atlantic right whales left in the world, including just 100 potential mothers.

“At the rate we are killing them off, this 100 females will be gone in 20 years,” said Mark Baumgartner, a marine ecologist at the Woods Hole Oceanographic Institution in Massachusetts. Without action, he warned, North Atlantic right whales will be functionally extinct by 2040.

Quick guide

Why are whales still endangered?

Population recovery will take decades

Commercial whaling on a large scale took place for three centuries until banned in 1986. Most whale populations had been reduced to such low levels that it will take decades for many of them to recover. Additional problems of entanglement, pollution, climate change and ship strikes are also curtailing their recovery.

Other threatened species include: the vaquita, a rare species of porpoise found in the gulf of California and rated the most endangered cetacean in the world – it is thought that only 30 or so remain in the wild; the blue whale, pictured, the largest animal ever known to have existed – between 10,000 and 25,000 remain; and the sei whale, the third-largest whale, with a population of around 80,000.

Photograph: Franco Banfi/WaterFrame RM

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A 10-year-old female was found dead off the Virginia coast in January, entangled in fishing gear, in the first recorded death of 2018. That followed a record 18 premature deaths in 2017, Baumgartner said.

Woods Hole and other groups, including the National Oceanic and Atmospheric Administration, have been tracing right whale numbers in earnest since the mid-1980s.

Federal research suggests 82% of premature deaths are caused by entanglement in fishing line. The prime culprit is the New England lobster industry. Crab fishing in Canadian waters is another cause of such deaths.

A lobster fisherman in Maine. Right whales can become entangled in the ropes used for fishing. Photograph: Daniel Grill/Tetra Images/Getty Images/Tetra images RF

Baumgartner said that until about seven years ago, the population of North Atlantic right whales was healthy. But then lobster fishermen began greatly increasing the strength of ropes used to attach lobster pots to marker buoys.

Whales becoming entangled are now far less able to break free, Baumgartner said. Some are killed outright, others cannot swim properly, causing them to starve or to lose so much blubber that females become infertile.

“Lobster and crab fishing and whales are able to comfortably co-exist,” Baumgartner said. “We are trying to propose solutions, it’s urgent.”

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Baumgartner said the US government should intervene to regulate fishing gear. He also said the industry should explore technology enabling fishermen to track and gather lobster pots without using roped buoys.

The whales migrate seasonally between New England and Florida, calving off Florida and Georgia from November to February. They primarily feed on phytoplankton. Scientists believe rapid warming of the Gulf of Maine, linked to climate change, is drastically depleting that food source.

Past measures to prevent ship collisions and to safeguard feeding areas have helped. Several environmental groups have sued the federal government, demanding greater protection for right whales.